H. Taxon: 7 



of preparing the slide f of photographing. This difference, together with 

 the round shape of the cysts, permits the identification of H. rostochi - 

 ensis and H. punctata from examination of the cysts alone. 



The Larvae 



Larval characters used in the key are average length, relation of body 

 length to bi'eadth, sb-ape of stylet knobs, location of the dorsal gland 

 orifice, and relation of the tail terminal to the stylet length. 



Identification by average length of the larvae has distinct limitations 

 due to the fact that variation in length within a species might be as 

 much as 20^ of the total length. Relation of larval length to width is 

 useful for separation of only one species, H. leptonepia . 



Stylet knobs are of two general types, concave anteriorly and convex 

 anteriorly. With most species, there is no doubt as to the type of 

 knobs, since the concavity or convexity is distinct, but some forms have 

 stylet knobs intermediate in type and difficult to distinguish. 



Location of the dorsal gland orifice is used mostly to distinguish be- 

 tween H, trifolii and H. glycines . As was pointed out by HLrschmann 

 (1956), the dorsal gland orifice in larvae of H. glycines is located 3«0 

 to 5.2 microns posterior to the stylet knobs; in H. trifolii , the loca- 

 tion is 5.6 microns posterior to the stylet knobs. 



The tail terminal is defined as the hyaline portion of the tail posterior 

 to the body cavity. This portion of the tail is usually clearly defined, 

 since the contents of the body cavity are more or less granular. In 

 poorly preserved specimens, the body contents may be shrunken, making the 

 tail terminal appear longer than it is in reality. 



Key to The Mature Qysts of Species of Heterodera 



Note: This key is designed to facilitate identification of the species 



of Heterodera , using only characters of the mature cysts and 

 their contents, that is, f^ggs with second stage larvae. Certain char- 

 acters used in the key may not be visible on other than fully mature 

 cysts. 



Measurements of larvae are from Fenwick and Franklin (1951) for most 

 species, from Jones (1951) for H. carotae , from Ichinohe (1952) for H. 

 glycines , and from Kirianova for H. fici. 



1. Body of cyst ovoid to globular, that is with posterior portion 

 rounded and vulva not located on a distinct protuberance (figs. 1 

 and 2) Heterodera rostochiensis group U. 



Body of cyst lemon-shaped, that is, with vulva located on a dis- 

 tinct protuberance (figs. 3 and 6) 2 



